The long-term goal of the current research is to understand the neural pathways and mechanisms underlying motivated behaviors, and specifically those that mediate the expression of male sexual behavior. Male sexual behavior is a complex behavior dependent on both intrinsic and external factors. While much research has focused on the role of olfactory or hormonal signals, much less is known about the influence of genitosensory or hormonal signals, much less is known about the influence of genitosensory cues in the control of male sexual behavior. The aim of the present proposal is to delineate the neural pathway by which genitosensory input related to population reaches motivation centers in the forebrain, and investigate the functional role of this pathway in male sexual behavior. Previous work from our laboratory has demonstrated the existence of a neural subcircuit in the forebrain that is specifically related to ejaculation in male rats. Our preliminary work has provided strong evidence for a candidate pathway that may relay ejaculation-specific genitosensory input to this subcircuit. This pathway includes a subset of neurons in the lumbar spinal cord that project to a specific thalamic nucleus, which in turn, projects to forebrain regions critical for sexual behavior. The current proposal will confirm the existence of this pathway and address three additional questions: (1) Which peripheral nerves and interneurons convey genitosensory information from the male reproductive organs to the lumbar spinal cord? (2) Does this pathway convey genitosensory stimuli associated specifically with ejaculation? (3) Is relay of this genitosensory information critical for the expression of male sexual behavior? These studies will shed light on an issue of long standing interest and fascination, namely the neurobiological basis of sexual pleasure. The proposed experiments, focusing on pathway conveying afferent genitosensory information, will fill a crucial gap in our understanding of the motivational circuitry mediating sexual behavior. Since neural mechanisms controlling ejaculation in humans are similar to that in the rat, results of these experiments will have relevance to our understanding of human sexual dysfunction and may contribute to the development of new therapeutic approaches.